The objectives of this study are to examine the hypotheses that: 1) adaptive changes in response to intestinal bypass take place in the smooth muscle of the small intestine, and 2) suspected changes are due to local as well as systemic factors. These hypotheses will be tested by determining physiological, anatomical, and biochemical parameters in intestinal smooth muscle after operation and after various regimens of feeding, hormone infusion and/or pharmacological manipulations. Small bowel bypass will be performed in rats. The smooth muscle and mucosa will be evaluated at 3, 14 and 35 days after operation in both the bypassed and the incontinuity segments. Physiological changes in muscle activity will be determined by monitoring the transit of a nonabsorbable marker through the intestinal lumen, the intestinal myoelectric activity and the contractile activities of isolated strips of smooth muscle. Anatomical changes will be determined by measuring the size and weight of the mucosa and muscle layers and the size of individual muscle cells. Biochemical changes will be determined by measuring the contents of total protein, contractile proteins, collagen; the levels of adenosine triphosphate, creatine phosphate, glycogen and lactic acid; and the levels of cytochrome c and the respiratory capacity. Local factors will be varied by feeding with total parenteral nutrition or with elemental diets to which various quantities of alpha-cellulose have been added. Systemic factors will be varied by infusing various hormones (gastrin, secretin cholecystokinin, etc) or pharmacological agents. Results of this study should establish whether the smooth muscle of the intestine is involved in any of the adaptive changes that occur in intestinal segments which have been bypassed or in segments which remain incontinuity with the rest of the gastrointestinal tract. In addition, these data should add to our limited knowledge on the growth, development, and metabolism of intestinal smooth muscle.